Shagged the Thread

Had a bit of a problem last night, where the collet on the CNC router went on smoothly, but after a cutting job, it had jammed on solidly.  I suspect the collet was slightly oversized (or heated up more than the threaded shaft) and slipped a thread, causing a cross-threaded situation.

In any case, what it meant that once I managed to get the collet off, the thread on the router shaft was shagged.  Badly.

Crap.

In hindsight, if I had known it was going to be that bad, I would have been better off grinding a gouge in the collet, and used a nut cracker to snap the collet in two to remove it.  Hindsight is so 20:20


In any case, I now had a threaded shaft that nothing could be screwed onto.  I went shopping around for a die (as in a tap & die), but finding one that was 25mm proved a bit tricky.  Tried Total Tools, but not only did they not have anything close to the size I needed, but the guy serving me didn’t even know how to use a digital caliper.  How can you work in a tool shop, and not be able to use such a fundamental tool?

I ended up having a chat with one of the fitters in the mechanical workshop at work, and while they didn’t have an odd shaped die, they were able to lend me a thread file, and some lapping paste.


The thread file worked a treat, getting the thread to the point that I could get a collet threaded on.  Still bloody tight.  But what really fixed things up was the second stage, adding some lapping paste to the threads, and running the collet on and off the shaft.  And it worked.  After an hour or so of threading it on and off, cleaning, filing, I had the thread back to being about as smooth as it was, if not better.

The thread has been damaged a bit from the experience, but at least I have been able to recover it enough to be operational again.

Ever heard of a polissoir?

No, me neither!  Although in saying that, it was probably referred to in the bible for finishing: A Polishers Handbook, by Neil Ellis.  If you haven’t read or come across this before, it is well work the small investment. You can order it here.

And no, there is nothing behind that endorsement, other than it being highly recommended, and essential reading matter.

In saying that, seeing as there is a new edition (much newer than my current copy), and I don’t remember whether polissoirs are mentioned, it might be time for me to be reacquainted with it as well.

front cover 25%.jpeg

back cover 25%.jpeg

Anyway, back to the polissior.

It is an 18th century tool (if not from even earlier) for applying, abrading and polishing a wax finish.  Simply made from a tightly bound bundle of organic material (such as straw), it is then dipped in molten wax to charge it up, and then (once cooled) rubbed over the surface of the timber.

Polissoirs_001_adj.jpgThe polissior both burnishes the surface, and applies the wax, driving it into the pores (where open grain timber is used).

The excess wax is removed, either with a wooden scraper (or the other end of the polissior), then the surface buffed with a cloth.

There are a few on the market, such as the one pictured above from Skagit BroomWorks and Henry Eckert Fine Tools have a version as well.

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